- LiveInterval& PI = LI.getOrCreateInterval(DestReg);
- unsigned pIdx = LI.getDefIndex(LI.getInstructionIndex(P));
- VNInfo* PVN = PI.getLiveRangeContaining(pIdx)->valno;
- PhiValueNumber.insert(std::make_pair(DestReg, PVN->id));
-
- // PHIUnion is the set of incoming registers to the PHI node that
- // are going to be renames rather than having copies inserted. This set
- // is refinded over the course of this function. UnionedBlocks is the set
- // of corresponding MBBs.
- std::map<unsigned, unsigned> PHIUnion;
- SmallPtrSet<MachineBasicBlock*, 8> UnionedBlocks;
-
- // Iterate over the operands of the PHI node
- for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
- unsigned SrcReg = P->getOperand(i-1).getReg();
-
- // Check for trivial interferences via liveness information, allowing us
- // to avoid extra work later. Any registers that interfere cannot both
- // be in the renaming set, so choose one and add copies for it instead.
- // The conditions are:
- // 1) if the operand is live into the PHI node's block OR
- // 2) if the PHI node is live out of the operand's defining block OR
- // 3) if the operand is itself a PHI node and the original PHI is
- // live into the operand's defining block OR
- // 4) if the operand is already being renamed for another PHI node
- // in this block OR
- // 5) if any two operands are defined in the same block, insert copies
- // for one of them
- if (isLiveIn(SrcReg, P->getParent(), LI) ||
- isLiveOut(P->getOperand(0).getReg(),
- MRI.getVRegDef(SrcReg)->getParent(), LI) ||
- ( MRI.getVRegDef(SrcReg)->getOpcode() == TargetInstrInfo::PHI &&
- isLiveIn(P->getOperand(0).getReg(),
- MRI.getVRegDef(SrcReg)->getParent(), LI) ) ||
- ProcessedNames.count(SrcReg) ||
- UnionedBlocks.count(MRI.getVRegDef(SrcReg)->getParent())) {
-
- // Add a copy for the selected register
- MachineBasicBlock* From = P->getOperand(i).getMBB();
- Waiting[From].insert(std::make_pair(SrcReg, DestReg));
- UsedByAnother.insert(SrcReg);
- } else {
- // Otherwise, add it to the renaming set
- LiveInterval& I = LI.getOrCreateInterval(SrcReg);
- unsigned idx = LI.getMBBEndIdx(P->getOperand(i).getMBB());
- VNInfo* VN = I.getLiveRangeContaining(idx)->valno;
-
- assert(VN && "No VNInfo for register?");
-
- PHIUnion.insert(std::make_pair(SrcReg, VN->id));
- UnionedBlocks.insert(MRI.getVRegDef(SrcReg)->getParent());
- }
- }
-
- // Compute the dominator forest for the renaming set. This is a forest
- // where the nodes are the registers and the edges represent dominance
- // relations between the defining blocks of the registers
- std::vector<StrongPHIElimination::DomForestNode*> DF =
- computeDomForest(PHIUnion, MRI);
-
- // Walk DomForest to resolve interferences at an inter-block level. This
- // will remove registers from the renaming set (and insert copies for them)
- // if interferences are found.
- std::vector<std::pair<unsigned, unsigned> > localInterferences;
- processPHIUnion(P, PHIUnion, DF, localInterferences);
-
- // If one of the inputs is defined in the same block as the current PHI
- // then we need to check for a local interference between that input and
- // the PHI.
- for (std::map<unsigned, unsigned>::iterator I = PHIUnion.begin(),
- E = PHIUnion.end(); I != E; ++I)
- if (MRI.getVRegDef(I->first)->getParent() == P->getParent())
- localInterferences.push_back(std::make_pair(I->first,
- P->getOperand(0).getReg()));
-
- // The dominator forest walk may have returned some register pairs whose
- // interference cannot be determined from dominator analysis. We now
- // examine these pairs for local interferences.
- for (std::vector<std::pair<unsigned, unsigned> >::iterator I =
- localInterferences.begin(), E = localInterferences.end(); I != E; ++I) {
- std::pair<unsigned, unsigned> p = *I;
-
- MachineDominatorTree& MDT = getAnalysis<MachineDominatorTree>();
-
- // Determine the block we need to scan and the relationship between
- // the two registers
- MachineBasicBlock* scan = 0;
- unsigned mode = 0;
- if (MRI.getVRegDef(p.first)->getParent() ==
- MRI.getVRegDef(p.second)->getParent()) {
- scan = MRI.getVRegDef(p.first)->getParent();
- mode = 0; // Same block
- } else if (MDT.dominates(MRI.getVRegDef(p.first)->getParent(),
- MRI.getVRegDef(p.second)->getParent())) {
- scan = MRI.getVRegDef(p.second)->getParent();
- mode = 1; // First dominates second
- } else {
- scan = MRI.getVRegDef(p.first)->getParent();
- mode = 2; // Second dominates first
- }
-
- // If there's an interference, we need to insert copies
- if (interferes(p.first, p.second, scan, LI, mode)) {
- // Insert copies for First
- for (int i = P->getNumOperands() - 1; i >= 2; i-=2) {
- if (P->getOperand(i-1).getReg() == p.first) {
- unsigned SrcReg = p.first;
- MachineBasicBlock* From = P->getOperand(i).getMBB();
-
- Waiting[From].insert(std::make_pair(SrcReg,
- P->getOperand(0).getReg()));
- UsedByAnother.insert(SrcReg);
-
- PHIUnion.erase(SrcReg);
- }
- }